The hard disk drive (HDD) has spread widely as a memory device in computers and has become one memory device which cannot be missing from current computer systems. In addition, the applications of HDDs, such as in dynamic image storage and playback devices, car navigation systems, or portable telephones, are even more widespread because of the superior characteristics of the HDD.
The magnetic disk used in an HDD has a plurality of data tracks and a plurality of servo tracks formed in concentric circles. A plurality of data sectors which include user data is provided in each data track. Each servo track has address information. A servo track is constructed from a plurality of servo data arranged separately in the circumferential direction, and one or a plurality of data sectors is formed between the servo data. A data write to a data sector and a data read from a data sector can be conducted when a head element accesses the desired data sector in accordance with the address information of the servo data.
A head element is formed on a slider, and the slider is secured onto the suspension of an actuator. The assembly of the actuator and the head slider is referred to as the head stack assembly (HSA). In addition, the assembly of the suspension and the head slider is referred to as the head gimbal assembly (HGA). The head slider can fly above a magnetic disk because the pressure due to the viscosity of the air between the slider air bearing surface opposite the magnetic disk and the rotating magnetic disk is balanced by the pressure applied in the direction of the magnetic disk by the suspension. The head slider moves to the target track and is positioned above that track when the actuator rotates with the rotation shaft at the center.
As the tracks per inch (TPI) of a magnetic disk increase, improved accuracy in positioning the head slider is sought. However, the drive of the actuator by a voice coil motor (VCM) has limited positioning accuracy. Thus, technology for a two-stage actuator has been proposed in which a small actuator (micro-actuator) is installed on the front end of the actuator, and more accurate positioning is carried out.
Furthermore, one technology for substantially improving the recording density and the bits per inch (BPI) in the circumferential direction of a magnetic disk is thermally assisted recording. Thermally assisted recording applies heat of at least 200° C. and a magnetic field to a very small region of approximately several tens of nanometers by several tens of nanometers on a magnetic disk, and records data on the magnetic disk. Using the conversion of laser light to near field light by a near field optical element positioned in the vicinity of the recording magnetic pole is being considered as a mechanism for heating this very small region. A laser diode (LD) which is positioned on the back side of the air bearing surface of the head slider with a sub-mount in between is being studied as the light source.
The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.